Narrative:

We were at FL410 on direct route from ssm to roberts, destination stl. ZMP ATC cleared air carrier X to descend to FL390, 'need you down now due to traffic'. Pilot returned call of 'out of 410 for 390'. We heard no reply so called with descent a second time. Still no reply from ATC so we stayed at 410 trying to get confirmation of clearance. We tried 2 more times to confirm clearance to 390 but no reply. After about 1 min, ATC called and asked if we were still at 410. We said yes and had been trying to call to confirm we were actually cleared to 390. They gave us an immediate turn to west for traffic avoidance. A few mins later someone else from ATC asked us to call by phone during business hours. Calls were made and tapes replayed. After this first clearance to 390, reply was 'leaving 410 for 390'. There were no other transmissions heard on tape from us even though we made 3 more trying to get confirmation for descent. We felt our reply to leaving 410 should have been acknowledged by ATC but 'they' said once controller hears flight give correct response (leaving 410 for 390) they do not have any obligation to respond to us. With numerous altitude deviations, it is hard to believe that they have no obligation to respond to a pilot's mandatory call of 'leaving an altitude'. ATC said no violations were filed which leads me to believe they realize they had a problem in their operation which also needed correcting. Supplemental information from acn 181015: during cruise at FL410 while speaking to msp center a clearance was apparently issued to my flight requesting that we descend to FL390. I reported back with the statement that we were out of FL410 for FL390. No acknowledgement was heard and I became concerned that the descent clearance was perhaps not for us. I looked at the PF and indicated my uncertainty and we decided to stay at FL410 until confirmation could be made. I made at least 3 more calls attempting to confirm our descent and/or acknowledge our readback but no response was heard. I then called and advised ATC that we would be staying at FL410 until confirmation could be made that the clearance was indeed for our flight. We were immediately informed that the descent was for us but now to turn right heading 280 degree. An appropriate turn was then given to the apparent conflicting traffic. The captain spoke with the supervisor and listened to the ATC tape which he recorded for himself. The captain played the tape on the phone to me and it was clear that the controller heard my initial readback, 'out of FL410 for FL390'. None of the other attempts we made were received other than a portion of a confirmation attempt of which only 'out of FL410 for FL390' was heard again. It was then understandable why the ATC supervisor wanted us to call. The possible pilot deviation was resolved through good communication by phone between the crew and the ATC personnel at msp center, however, it occurred due to my not prefixing my original readback with the word 'confirm' or just 'say again for (our flight)'. I feel more careful phraseology coupled with some improvement in eliminating being 'stepped on' in our current communication system would benefit everyone and enhance safety.

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Original NASA ASRS Text

Title: ACR X NON ADHERENCE TO ATC CLRNC FAILED TO LEAVE ALT AFTER RPTING LEAVING ALT FOR NEW ASSIGNED ALT.

Narrative: WE WERE AT FL410 ON DIRECT RTE FROM SSM TO ROBERTS, DEST STL. ZMP ATC CLRED ACR X TO DSND TO FL390, 'NEED YOU DOWN NOW DUE TO TFC'. PLT RETURNED CALL OF 'OUT OF 410 FOR 390'. WE HEARD NO REPLY SO CALLED WITH DSCNT A SECOND TIME. STILL NO REPLY FROM ATC SO WE STAYED AT 410 TRYING TO GET CONFIRMATION OF CLRNC. WE TRIED 2 MORE TIMES TO CONFIRM CLRNC TO 390 BUT NO REPLY. AFTER ABOUT 1 MIN, ATC CALLED AND ASKED IF WE WERE STILL AT 410. WE SAID YES AND HAD BEEN TRYING TO CALL TO CONFIRM WE WERE ACTUALLY CLRED TO 390. THEY GAVE US AN IMMEDIATE TURN TO W FOR TFC AVOIDANCE. A FEW MINS LATER SOMEONE ELSE FROM ATC ASKED US TO CALL BY PHONE DURING BUSINESS HOURS. CALLS WERE MADE AND TAPES REPLAYED. AFTER THIS FIRST CLRNC TO 390, REPLY WAS 'LEAVING 410 FOR 390'. THERE WERE NO OTHER TRANSMISSIONS HEARD ON TAPE FROM US EVEN THOUGH WE MADE 3 MORE TRYING TO GET CONFIRMATION FOR DSCNT. WE FELT OUR REPLY TO LEAVING 410 SHOULD HAVE BEEN ACKNOWLEDGED BY ATC BUT 'THEY' SAID ONCE CTLR HEARS FLT GIVE CORRECT RESPONSE (LEAVING 410 FOR 390) THEY DO NOT HAVE ANY OBLIGATION TO RESPOND TO US. WITH NUMEROUS ALT DEVS, IT IS HARD TO BELIEVE THAT THEY HAVE NO OBLIGATION TO RESPOND TO A PLT'S MANDATORY CALL OF 'LEAVING AN ALT'. ATC SAID NO VIOLATIONS WERE FILED WHICH LEADS ME TO BELIEVE THEY REALIZE THEY HAD A PROBLEM IN THEIR OP WHICH ALSO NEEDED CORRECTING. SUPPLEMENTAL INFO FROM ACN 181015: DURING CRUISE AT FL410 WHILE SPEAKING TO MSP CENTER A CLRNC WAS APPARENTLY ISSUED TO MY FLT REQUESTING THAT WE DSND TO FL390. I RPTED BACK WITH THE STATEMENT THAT WE WERE OUT OF FL410 FOR FL390. NO ACKNOWLEDGEMENT WAS HEARD AND I BECAME CONCERNED THAT THE DSCNT CLRNC WAS PERHAPS NOT FOR US. I LOOKED AT THE PF AND INDICATED MY UNCERTAINTY AND WE DECIDED TO STAY AT FL410 UNTIL CONFIRMATION COULD BE MADE. I MADE AT LEAST 3 MORE CALLS ATTEMPTING TO CONFIRM OUR DSCNT AND/OR ACKNOWLEDGE OUR READBACK BUT NO RESPONSE WAS HEARD. I THEN CALLED AND ADVISED ATC THAT WE WOULD BE STAYING AT FL410 UNTIL CONFIRMATION COULD BE MADE THAT THE CLRNC WAS INDEED FOR OUR FLT. WE WERE IMMEDIATELY INFORMED THAT THE DSCNT WAS FOR US BUT NOW TO TURN R HDG 280 DEG. AN APPROPRIATE TURN WAS THEN GIVEN TO THE APPARENT CONFLICTING TFC. THE CAPT SPOKE WITH THE SUPVR AND LISTENED TO THE ATC TAPE WHICH HE RECORDED FOR HIMSELF. THE CAPT PLAYED THE TAPE ON THE PHONE TO ME AND IT WAS CLR THAT THE CTLR HEARD MY INITIAL READBACK, 'OUT OF FL410 FOR FL390'. NONE OF THE OTHER ATTEMPTS WE MADE WERE RECEIVED OTHER THAN A PORTION OF A CONFIRMATION ATTEMPT OF WHICH ONLY 'OUT OF FL410 FOR FL390' WAS HEARD AGAIN. IT WAS THEN UNDERSTANDABLE WHY THE ATC SUPVR WANTED US TO CALL. THE POSSIBLE PLTDEV WAS RESOLVED THROUGH GOOD COM BY PHONE BTWN THE CREW AND THE ATC PERSONNEL AT MSP CENTER, HOWEVER, IT OCCURRED DUE TO MY NOT PREFIXING MY ORIGINAL READBACK WITH THE WORD 'CONFIRM' OR JUST 'SAY AGAIN FOR (OUR FLT)'. I FEEL MORE CAREFUL PHRASEOLOGY COUPLED WITH SOME IMPROVEMENT IN ELIMINATING BEING 'STEPPED ON' IN OUR CURRENT COM SYS WOULD BENEFIT EVERYONE AND ENHANCE SAFETY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.